The nature of rainfall in the main drainage sub-basins of Uganda

Figures & data

Fig. 1 Map of Uganda showing the distribution of observatories and the size of the main drainage sub-basins. Source of original map: MWE (2005).

Fig. 2 Data preprocessing steps and analysis used in the study.

Table 1 Basic statistical characteristics of annual rainfall data for the 35 stations in the seven drainage sub-basins in the period 1940–2009.

Station	Mean rainfall	Highest total rainfall (mm)	Year of occurrence	Lowest total rainfall (mm)	Year of occurrence	SD	Serial corr. coeff. (95%)	von-Neumann ratio (95%)	CV (%)
Aswa
Morulem	1130	1672	1961	877	1968	15	0.2	1.4	15
Kitgum Center	1318	2042	1970	733	1918	21	0.17	1.6	18
Patong	1233	1920	1978	755	1959	21	0.2	1.4	21
Lake Victoria
Entebbe Int. Airport	1617	2679	1999	1121	2004	24	0.17	1.6	18
Jinja	1312	1972	1963	871	1953	21	0.3	1.3	20
Mbarara Met	940	1522	1951	696	1952	13	0	2	17
Katigondo WFM	1222	2032	1984	753	1967	23	0.3	1.3	22
Kamenyamigo	1012	1506	1951	569	1992	17	0.2	1.5	21
Rwoho Forest	985	1606	1951	540	1981	18	0.3	1.2	22
Bakijulula	1225	1987	1987	854	1989	18	0.3	1.3	17
Victoria Nile
Aduku Variety	1331	1712	1967	985	1952	13	0.2	1.5	12
Kakooge Gombol	1013	1695	1947	374	1974	27	0.3	1.2	29
Kawanda Res	1244	1737	1961	783	1983	20	0.2	1.5	20
Namulonge Res	1217	1747	1997	674	1989	18	0.3	1.2	17
Gulu Met	1559	2040	1970	1002	1943	20	0.06	1.8	15
Ngetta Farm	1447	1930	1963	1157	1973	15	0.09	1.8	13
Lake Edward
Kasese Met	897	1151	1993	676	1991	11	−0.1	2.2	14
Kabale Met	1021	1477	1945	768	1948	12	0.17	1.6	14
Kachwekano DFI	1041	1480	1996	707	1960	13	0.24	1.5	15
Kirima Forest	1135	1526	1996	844	1969	13	−0.09	2.1	13
Rwashamaire	1025	1401	1951	709	1946	15	0.3	1.2	18
Lake Albert
Masindi Met	1329	1733	1972	1014	1983	15	0.19	1.57	13
Kijura Factory	1518	2024	1961	1147	1945	17	0.14	1.6	14
Bulindi Farm	1342	2465	1984	1020	1957	24	0.19	1.6	21
Albert Nile
Arua	1443	1908	1955	1046	1931	15	0.2	1.4	13
Nebbi UTC	1064	1590	1961	585	1970	20	0.5	0.8	22
Moyo Boma	1309	1973	1951	875	1970	21	0.17	1.67	18
Lake Kyoga
Tororo Met	1462	1981	1961	879	1949	20	0.29	1.3	17
Mutai Forest	1359	2238	1961	943	1973	18	0.04	1.9	15
Mukono Agric	1355	2244	1960	772	1972	26	0.5	0.8	23
Kangole	660	1089	1961	410	1962	14	0.02	2	25
Serere Agric.	1376	2378	1996	939	1939	19	0	2	16
Soroti Met	1336	2032	1915	851	1957	21	0.1	1.7	19
Kibale VTC	1361	2047	1961	626	1980	21	0.06	1.9	18
Mbale	1224	1789	1951	807	1927	19	0.16	1.7	19
Kotido	677	1145	1946	351	1965	16	0.15	1.7	28

Fig. 3 Regional total rainfall (mm) for the period 1940–2009.

Fig. 4 Seasonal cycle in Ugandan rainfall between the seven sub-basins.

Fig. 5 Variation of rainfall in the main drainage sub-basins in Uganda 1940–2009. Variability is expressed as percentage of CV at rainfall stations.

Table 2 Results from PCI calculations using temporal and seasonal concentration methods.

Sub-basin	1940–2009		1940–1969		1970–1999
	Seasonal	Temporal	Seasonal	Temporal	Seasonal	Temporal
Albert Nile	10.57	1.44	10.49	3.38	10.70	3.35
Lake Albert	9.71	1.44	9.60	3.37	9.85	3.35
Aswa	10.91	1.46	10.93	3.39	10.92	3.39
Lake Edward	9.62	1.43	9.70	3.35	9.56	3.35
Lake Kyoga	9.76	1.44	9.79	3.37	9.75	3.36
Lake Victoria	9.67	1.44	9.69	3.37	9.73	3.36
Victoria Nile	9.26	1.44	9.25	3.37	9.32	3.35

Fig. 6 Distribution of long-term mean monthly rainfall (mm) in the sub-basins of Uganda from 1940 to 2009.

Table 3 Temporal rainfall characteristics in the main drainage sub-basins of Uganda.

		Albert Nile		River Aswa		Lake Albert		Lake Edward		Lake Kyoga		Lake Victoria		Victoria Nile
		Z	Qi	Z	Qi	Z	Qi	Z	Qi	Z	Qi	Z	Qi	Z	Qi
January	1940–2009	1.42	0.02	2.05	0.01	0.65	0.01	0.08	0.00	1.14	0.04	0.46	0.01	1.01	0.02
	1940–1969	–0.43	–0.02	0.41	0.01	0.43	0.03	–0.48	–0.03	0.11	0.03	–0.64	–0.07	–0.25	–0.04
	1970–1999	1.27	0.04	0.79	0.00	–0.11	–0.01	0.46	0.06	0.71	0.09	0.24	–0.01	–0.29	–0.02
Year of …..rainfall	Max	1955		1977		1963		1998		1970		1963		1963
	Min	1946		1946		1946		1983		1968		1989		1949
February	1940–2009	0.57	0.00	1.16	0.00	0.46	0.00	-0.37	0.00	0.85	0.01	–0.83	–0.01	–1.22	–0.03
	1940–1969	0.23	0.01	1.11	0.06	–0.43	–0.03	1.27	0.07	1.03	0.26	0.96	0.08	1.25	0.17
	1970–1999	0.05	0.00	–0.92	–0.02	–0.54	–0.04	–0.43	–0.03	0.14	0.02	0.31	0.01	–1.14	–0.11
Year of …..rainfall	Max	1969		1968		1979		1979		1978		1964		1964
	Min	1945		1946		1962		1997		1962		1989		1946
March	1940–2009	–0.15	0.00	-0.17	0.00	0.40	0.00	1.36	0.01	0.84	0.02	1.61	0.04	0.27	0.01
	1940–1969	–0.04	–0.00	0.18	0.00	0.89	0.04	0.12	0.00	1.64	0.29	1.21	0.10	2.03	0.19
	1970–1999	–0.04	0.00	–0.40	0.00	0.61	0.04	0.79	0.07	0.50	0.10	–0.03	–0.00	0.43	0.04
Year of …..rainfall	Max	1957		1970		1985		1974		1970		1978		1960
	Min	1953		1945		1946		1982		1973		1949		1949
April	1940–2009	–0.49	–0.00	1.54	0.01	0.51	0.00	–1.15	–0.01	0.02	0.00	–0.72	–0.01	–1.88	-0.04
	1940–1969	–1.57	–0.06	0.00	0.00	0.75	0.03	0.41	0.02	0.11	0.01	0.00	0.01	0.71	0.06
	1970–1999	–1.48	0.05	0.43	0.00	–0.89	–0.05	–1.25	–0.11	1.39	0.17	–0.34	–0.02	–0.25	0.03
Year of …..rainfall	Max	1947		1946		1963		1982		1947		1963		1966
	Min	1969		1969		1945		1999		1969		1952		1945
May	1940–2009	–1.83	–0.02	–0.41	0.00	0.72	0.00	0	0.00	–0.19	0.00	–0.90	–0.02	–0.43	–0.01
	1940–1969	–1.32	–0.07	–1.03	–0.03	–1.46	–0.08	–0.55	–0.03	0.11	0.04	–1.36	–0.15	–1.32	–0.09
	1970–1999	1.07	–0.05	–2.78	–0.07	–0.62	–0.02	0.11	0.02	–0.25	0.03	–0.17	–0.01	0.61	0.04
Year of …..rainfall	Max	1946		1985		1962		1993		1954		1945		1957
	Min	1971		1966		1966		1984		1966		1960		1966
June	1940–2009	–0.29	0.00	0.78	0.00	0.57	0.00	–0.09	0.00	0.17	0.00	0.21	0.01	–0.90	–0.02
	1940–1969	–1.43	–0.08	–1.18	–0.04	–0.68	–0.05	–1.41	–0.06	–0.96	–0.12	0.07	0.01	0.64	0.05
	1970–1999	1.45	0.05	–0.77	–0.00	–0.07	–0.00	–0.11	–0.01	–1.18	–0.14	0.15	0.02	–1.11	–0.06
Year of …..rainfall	Max	1957		1985		1943		1972		1950		1974		1972
	Min	1952		1965		1949		1999		1960		1990		1952
July	1940–2009	1.07	0.01	1.81	0.01	0.19	0.00	0.05	0.00	–0.31	0.00	0.41	0.01	–0.72	–0.01
	1940–1969	–0.18	–0.01	–1.57	–0.04	–0.96	–0.05	–2.23	–0.07	–1.57	–0.15	–0.68	–0.05	–1.18	–0.05
	1970–1999	0.30	0.01	0.48	0.00	–0.68	–0.03	–1.68	–0.16	–0.29	0.07	0.03	0.00	–1.57	–0.14
Year of …..rainfall	Max	1998		1949		1984		1974		1974		1974		1974
	Min	1941		1963		1990		1993		1973		1993		1963
August	1940–2009	–1.05	–0.01	0.57	0.00	0.73	0.00	–0.31	0.00	–0.84	–0.01	–0.7	–0.02	–1.51	–0.03
	1940–1969	–0.43	0.03	–1.43	–0.03	–1.57	–0.05	–1.59	–0.08	–1.93	–0.24	–1.68	–0.15	–2.64	–0.20
	1970–1999	–1.59	–0.05	–0.59	–0.02	–0.14	–0.01	–1.61	–0.15	–0.29	–0.03	0.03	0.00	–0.79	–0.06
Year of …..rainfall	Max	1975		1946		1962		1976		1961		1988		1955
	Min	1951		1959		1967		1982		1969		1986		1965
September	1940–2009	–1.51	–0.00	0.79	0.00	0.59	0.00	–0.80	–0.01	–0.29	–0.00	0.39	0.01	0.62	0.01
	1940–1969	–0.61	–0.02	0.11	0.00	0.04	0.00	–1.95	–0.09	0.46	0.09	0.25	0.01	–0.07	–0.00
	1970–1999	–1.16	–0.04	–2.99	–0.06	–1.28	–0.04	–0.11	–0.01	–0.79	0.10	0.62	0.04	–0.21	–0.02
Year of …..rainfall	Max	1955		1973		1961		1992		1983		1955		2007
	Min	1965		1982		1953		1993		1957		1957		1963
October	1940–2009	0.76	0.00	1.88	0.01	1.94	0.02	0.79	0.01	1.09	0.04	2.47	0.05	2.02	0.04
	1940–1969	1.36	0.06	2.36	0.08	2.11	0.11	–1.98	–0.09	2.43	0.36	2.03	0.14	1.89	0.17
	1970–1999	1.23	0.03	–0.38	–0.00	1.71	0.08	2.43	0.12	1.39	0.19	1.25	0.06	1.36	0.12
Year of …..rainfall	Max	1965		1983		1965		1983		1972		1961		1961
	Min	1943		1943		1947		1963		1979		1943		1947
November	1940–2009	1.34	0.01	2.08	0.01	2.36	0.03	0.65	0.00	2.05	0.06	1.00	0.03	1.19	0.03
	1940–1969	1.21	0.06	0.39	0.02	1.71	0.10	0.16	0.00	0.68	0.14	1.86	0.25	1.57	0.18
	1970–1999	1.20	0.06	0.39	0.02	1.71	0.10	0.16	0.00	1.89	0.21	1.86	0.25	1.57	0.18
Year of …..rainfall	Max	1961		1961		1961		1987		1961		1961		1961
	Min	1950		1956		1943		1981		1950		1947		1947
December	1940–2009	2.11	0.02	0.37	0.00	0.17	0.00	0.13	0.00	0.72	0.02	0.84	0.02	0.30	0.01
	1940–1969	0.93	0.06	0.02	0.01	1.34	0.09	–0.34	–0.02	0.57	0.14	0.79	0.08	0.82	0.07
	1970–1999	3.30	0.08	2.34	0.05	2.41	0.09	1.53	0.08	2.28	0.21	1.60	0.07	1.64	0.12
Year of …..rainfall	Max	1951		1951		1965		1963		1951		1951		1951
	Min	1953		1943		1971		1970		1952		1952		1952
Annual	1940–2009	–0.98	–0.03	0.11	0.31	1.56	0.05	–0.69	–0.02	0.44	0.03	1.02	0.09	0.15	0.01
	1940–1969	0.21	0.03	0.11	0.03	0.93	0.21	–0.48	–0.09	1.68	0.73	0.79	0.24	1.36	0.53
	1970–1999	0.96	0.30	–2.13	–0.24	–0.36	–0.04	–1.46	–0.37	0.32	0.24	0.48	0.08	0.25	0.09
Year of …..rainfall	Max	1961		1977		1961		1996		1961		1951		1961
	Min	1971		1953		1983		1965		1980		1952		1983
DJF	1940–2009	0.77	0.01	1.21	0.08	0.24	0.00	0.04	0.00	0.61	0.04	0.52	0.02	0.21	0.11
	1940–1969	0.39	0.05	1.21	0.08	0.86	0.13	0.62	0.09	1.16	0.61	0.68	0.12	0.89	0.21
	1970–1999	2.11	0.18	0.52	0.02	0.68	0.06	1.00	0.12	1.75	0.45	1.08	0.09	0.68	0.12
Year of …..rainfall	Max	1969		1969		1969		1998		1969		1998		1998
	Min	1946		1946		1946		1992		1949		1946		1967
MAM	1940–2009	–1.62	–0.03	0.44	0.00	1.18	–0.02	–0.12	0.00	0.13	0.00	0.14	0.01	–0.61	–0.03
	1940–1969	–1.21	–0.14	–0.68	–0.04	–0.18	–0.02	0.59	0.07	1.07	0.37	–0.14	–0.02	1.03	0.18
	1970–1999	0.91	0.10	–1.67	–0.12	–0.39	–0.03	–0.86	–0.08	0.68	0.19	–0.17	–0.02	0.57	0.08
Year of …..rainfall	Max	1957		1982		1985		1967		1947		1963		1960
	Min	1971		1953		1955		1999		1973		1949		2007
JJA	1940–2009	–0.41	0.00	0.67	0.00	–0.51	–0.01	–0.71	–0.01	–0.58	–0.02	–0.33	–0.02	–1.43	–0.06
	1940–1969	–0.96	–0.12	–1.64	0.11	–1.96	–0.13	–1.62	–0.16	–2.43	–0.52	–1.14	–0.16	–1.64	–0.24
	1970–1999	–0.21	–0.02	–1.67	–0.09	–1.25	–0.11	–2.43	–0.41	–1.18	–0.22	–0.03	–0.01	–1.86	–0.25
Year of …..rainfall	Max	1961		1946		1984		1996		1961		1974		1961
	Min	1951		1959		1990		1965		1960		1960		1990
SON	1940–2009	0.78	0.01	2.64	0.03	2.99	0.06	0.56	0.00	1.30	0.06	1.65	0.07	2.07	0.08
	1940–1969	1.07	0.08	1.78	0.12	2.50	0.19	–1.41	–0.11	1.93	0.56	1.75	0.31	1.89	0.33
	1970–1999	1.30	0.07	–2.35	–0.13	1.00	0.07	021	0.04	1.28	0.36	–0.20	–0.02	1.03	0.14
Year of …..rainfall	Max	1961		1983		1961		1996		1961		1961		1961
	Min	1943		1943		1943		1979		1957		1957		1943
(sub-basin	Sen’s T	–0.31		–3.91		–3.13		–0.91		–1.09		–1.36		0.19

Fig. 7 Spatial distribution of negative (–) and positive (+) trends for annual total rainfall in the main drainage sub-basins in Uganda.

Fig. 8 Variations and trends in normalized annual rainfall anomalies series with nine-point Gaussian filter, over the main drainage sub-basins in Uganda.

Fig. 9 Spatial distribution of negative (–) and positive (+) trends for seasonal distribution of rainfall for the period 1940–2009 in the main drainage sub-basins of Uganda. Magnitude is in mm/season (not indicated on map).

Table 4 Coefficients of correlation between annual and seasonal rainfall departure series for main drainage sub-basins in Uganda.

	Albert Nile	River Aswa	Lake Albert	Lake Edward	Lake Kyoga	Lake Victoria	Victoria Nile
DJF	0.6	0.4	0.4	0.6	0.7	0.7	0.5
MAM	0.6	0.7	0.2	0.5	0.5	0.5	0.6
JJA	0.5	0.6	0.7	0.3	0.3	0.2	0.3
SON	0.6	0.6	0.4	0.7	0.4	0.5	0.5

MWE (Ministry of Water and Environment), 2005. Uganda National Water Development Report 2005. Kampala: Ministry of Water and Environment.

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